This application claims priority to German Patent Application DE 10 2007 041 805.3 filed Aug. 30, 2007, the entirety of which is incorporated by reference herein.
This invention relates to a method for machining the blade tips of the rotor wheel drums of turbomachines provided with integrally formed-on and/or separately assembled—conventional—blading, with the rotor wheel drum rotating in the process, and an apparatus for the performance of said method.
Rotor wheels of the compressors of turbomachines or rotor drums including several interconnected rotor wheels whose blades are retained on the disk periphery in a slot are, as is generally known, dry ground at the blade tips in a process in which the drum rotates at high speed. As during rotation in the installed state in the turbomachine, the blades retained in the slot are forced outwards by the centrifugal force, enabling the blade tips to be ground to the—minimum—clearance with the casing that is required in service to obtain high efficiency and high surge limit. Grinding the blade tips of the conventionally bladed drum rotating at high speed is further advantageous in that the blades are elastically retained during the machining process by the centrifugal force acting upon them, thereby preventing them from being excessively loaded.
Grinding of integrally manufactured rotor wheels (blisks), i.e. rotor wheels with rotor blades formed on the disk periphery or drums composed of two or more such rotor wheels, is problematic in that, in known high-velocity grinding, strong blade vibrations and the formation and flying of sparks with consequential damage to the blades are encountered.
On gas-turbine engines, it is known and advantageous to compose one and the same rotor wheel drum of the compressor of both integrally manufactured rotor wheels (blisks) and conventionally manufactured rotor wheels, which, moreover, may be made of different materials, for example titanium for the blisks and nickel-base material for the conventionally assembled blades. Due to the different designs, the respective materials and the different effects of the grinding process, either type of drum component and rotor wheel is individually machined in separate machining apparatuses, with assembly to be performed thereafter.